Occurrence of Grapevine Leafroll-Associated Virus-3 (GLRaV-3), Complete Nucleotide Sequence and Cultivar Susceptibility to a GLRaV-3 Isolate from Shaanxi Province of China

Grapevine (Vitis spp.) is globally one of the most economically important fruit crops. China is the largest grapevine-growing country of the world and Shaanxi province is one of the major grapevine-growing provinces in the country. A survey of GLRaV-3 found it widespread, with 57–100% infection frequencies, in both wine and table grapevine cultivars of three grapevine-growing regions of Shaanxi province. The virus infection frequencies varied with cultivars and regions. In order to obtain the full genomic length of a new GLRaV-3 isolate, GLRaV-3-Sau (accession number MK988555), was sequenced. This isolate has a genome of 18026 nucleotides, and 14 open reading frames (ORFs). The full-genome of the isolate GLRaV-3-Sau shared 85.88% nucleotide identity to GLRaV-3-LN, another isolate found in China. Coat protein (CP) genes of GLRaV-3 isolates were identical (99%) to the Vitis vinifera isolate (accession number HQ185608.1) from the USA. Immunohistochemistry for virus localization found that distribution patterns were similar in red-berried cultivar ‘Cabernet Sauvignon’ and white-berried cultivar ‘Chardonnay’, and GLRaV-3 is restricted in phloem tissue of vascular bundles. Virus transmission by micrografting found virus transmission efficiency was higher in ‘Chardonnay’ and ‘Thompson Seedless’ than in ‘Hunan-1’, indicating that ‘Hunan-1’ was less sensitive to GLRaV-3. As far as we know, these are the most comprehensive comparisons on the genome and CP genes of GLRaV-3 worldwide and the first to have found that the grapevine ‘Hunan-1’ is less susceptible to GLRaV-3.

Anatomical and Biochemical Traits Associated with Field Resistance of Onion Cultivars to Onion Thrips and the Effect of Mechanical Injury on the Level of Biochemical Compounds in Onion Leaves

Thrips tabaci Lind. is a global pest and also represents a serious threat to onion production in Poland. In 2 years (2015–2016) of field studies, 8 onion cultivars were evaluated to characterize the resistance to onion thrips and to determine if any biochemical and anatomical features of onion plants are associated with antixenotic and/or antibiotic mechanisms of resistance. Additionally, the influence of mechanical injury on the content of several biochemical compounds in onion leaves was made. The resistance to thrips colonization during the migration period, abundance, and thrips damage throughout the whole vegetation season was determined. We identified two cultivars, Tęcza and Wenta, resistant to thrips colonization and abundance, and one cultivar Wenta resistant to thrips damage. A positive correlation between concentrations of the reducing sugars and thrips abundance and conversely negative relationships between the total phenolic content and thrips damage was confirmed in both years. We suspect that a thinner epidermal layer, a smaller area of epidermal and mesophilic cells, and a lower diameter of vascular bundles may favor the resistance of onion cultivars to thrips. Thrips foraging resulted in a decrease in the content of soluble sugars, sucrose, and plant pigments in the leaves of all onion varieties.

High throughput phenotyping of cross-sectional morphology to assess stalk lodging resistance

Background Stalk lodging (mechanical failure of plant stems during windstorms) leads to global yield losses in cereal crops estimated to range from 5% to 25% annually. The cross-sectional morphology of plant stalks is a key determinant of stalk lodging resistance. However, previously developed techniques for quantifying cross-sectional morphology of plant stalks are relatively low-throughput, expensive and often require specialized equipment and expertise. There is need for a simple and cost-effective technique to quantify plant traits related to stalk lodging resistance in a high-throughput manner. Results A new phenotyping methodology was developed and applied to a range of plant samples including, maize (Zea mays), sorghum (Sorghum bicolor), wheat (Triticum aestivum), poison hemlock (Conium maculatum), and Arabidopsis (Arabis thaliana). The major diameter, minor diameter, rind thickness and number of vascular bundles were quantified for each of these plant types. Linear correlation analyses demonstrated strong agreement between the newly developed method and more time-consuming manual techniques (R2 > 0.9). In addition, the new method was used to generate several specimen-specific finite element models of plant stalks. All the models compiled without issue and were successfully imported into finite element software for analysis. All the models demonstrated reasonable and stable solutions when subjected to realistic applied loads. Conclusions A rapid, low-cost, and user-friendly phenotyping methodology was developed to quantify two-dimensional plant cross-sections. The methodology offers reduced sample preparation time and cost as compared to previously developed techniques. The new methodology employs a stereoscope and a semi-automated image processing algorithm. The algorithm can be used to produce specimen-specific, dimensionally accurate computational models (including finite element models) of plant stalks.

The Effect of Guttation on the Growth of Bamboo Shoots

Guttation is the process of exudating droplets from the tips, edges, and adaxial and abaxial surfaces of the undamaged leaves. Guttation is a natural and spontaneous biological phenomenon that occurs in a wide variety of plants. Despite its generally positive effect on plant growth, many aspects of this cryptic process are unknown. In this study, the guttation phenomenon characteristic of bamboo shoots and the anatomical feature of these and culm sheaths were systematically observed. In addition, the water transport pathway and the compounds in guttation droplets of bamboo shoots were analyzed, and the effect of bamboo sheaths’ guttation on the growth of bamboo shoots was assessed. The results revealed that bamboo shoots began to exudate liquid in the evening through to the next morning, during which period the volume of guttation liquid gradually increases and then decreases before sunrise. Many vascular bundles are in bamboo shoots and culm sheaths to facilitate this water transport. The exudate liquid contains organic acids, sugars, and hormones, among other compounds. Our findings suggest that the regular guttation of the sheath blade is crucial to maintain the normal growth of bamboo shoots.

Responses of the Lodging Resistance of Summer Maize with Different Gene Types to Plant Density

The appropriate increase of planting densities is the key to the obtainment of high-yield maize (Zea mays L.). However, lodging is a major constraint to limit grain yield under increased planting density in present maize production. Effects of population density on stalk lodging and agronomic traits were investigated using two maize cultivars Denghai 618 (DH618, low stalk with low spike height) and Xianyu335 (XY335, high stalk with high spike height). Four levels of density treatment were imposed by 1.5, 6.0, 7.5, and 9.0 × 104 plants ha−1. Results showed that bending strength, rind penetration strength, maximum bending strength, dry weight, and internode diameter of maize were significantly decreased with the increase of planting density. The change range of XY335 with the increase of planting density was significantly larger than that of DH618, showing a high sensitivity to planting density. In addition, the thickness of cortex and vascular bundle sclerenchyma cells was significantly reduced with the increase of planting density. Compared with 1.5 × 104 plants ha−1, the thickness of the above-ground third internode stem cortex was decreased by 9.64%, 12.72%, and 20.77% for DH618, and 19.26%, 30.49%, and 37.45% for XY335 at 6.0, 7.5, and 9.0 × 104 plants ha−1, respectively. The thickness of vascular bundle sclerenchyma cells at 1.5 × 104 plants ha−1 was decreased by 7.75%, 12.44%%, and 17.89% for DH618, 10.18%, 15.21%, and 24.73% for XY335, compared to those at 6.0, 7.5, and 9.0 × 104 plants ha−1, respectively. Visibly, with the increase of planting density, the thickness of cortex and vascular bundle sclerenchyma cells, and the number of vascular bundles were all significantly decreased, resulting in the increase of lodging rate. However, the extent of variation in these parameters for short-plant height hybrid was less than those for high-plant height hybrid, and the yield of short-plant height hybrid was greater than that of high-plant height hybrid, indicating that short-plant height hybrid has better resistance to lodging with higher yield at higher planting density. Therefore, lodging resistance and yield can be improved through selection and breeding strategies that achieving synergistic development of diameter, dry weight per unit, and cortex thickness in maize basal internodes.

The Pulp Stones: Morphological Analysis in Scanning Electron Microscopy and Spectroscopic Chemical Quantification

Background and objectives: Pulp stones are hard tissue structures formed in the pulp of permanent and deciduous teeth. Few studies have evaluated their morphology and chemical composition. However, their formation, composition, configuration and role played in overall health status are still unclear. Clinically, they may be symptomatic; technically, they impede access during endodontic therapy, increasing the risk of treatment errors. Thus, this study aimed to morphologically analyze pulp stones and present their chemical quantification, identifying their main chemical elements. It also correlates the results with their possible induction mechanisms. Materials and Methods: Seven pulp nodules were collected from molar teeth needing endodontic treatment. The morphology of the stones was analyzed by scanning electron microscopy (SEM), and their chemical composition was determined by X-ray dispersive energy spectroscopy (EDX). Results: These structures varied considerably in shape, size and topography. The site of the stones in the pulp cavity was the factor that most affected the morphology. The majority of the stones found in the pulp chambers presented nodular morphology, while those in the root canals presented a diffuse shape, resembling root canal anatomy. The topography of the nodules showed heterogeneous relief, revealing smooth and compact areas contrasting with the rugged and porous ones. The chemical composition varied depending on the location of the nodule in the pulp cavity and the relief of the analyzed area. Radicular stones presented considerably lower calcium and phosphorus content than coronary nodules. Conclusions: The high cellularity rate of the coronal pulp predisposes this region to nodular mineralizations around injured cells. The presence of larger caliber vascular bundles and higher collagen fiber content in radicular pulp determines a diffuse morphological pattern in this region. Understanding the morphology and chemical composition of the pulp stones allows future translational pathways towards the prevention or treatment of such conditions.

3D Visualization of Bamboo Node’s Vascular Bundle

The vascular bundle is an important structural unit that determines the growth and properties of bamboo. A high-resolution X-ray microtomography (μCT) was used to observe and reconstruct a three-dimensional (3D) morphometry model of the vascular bundle of the Qiongzhuea tumidinoda node due to its advantages of quick, nondestructive, and accurate testing of plant internal structure. The results showed that the morphology of vascular bundles varied significantly in the axial direction. In the cross-section, the number of axial vascular bundles reached a maximum at the lower end of the sheath scar, and the minimum of it was at the middle of the diaphragm. The frequency of axial vascular bundles decreased from the lower end of the node to the nodal ridge, and subsequently increased until the upper end of the bamboo node. The proportion of parenchyma, fibers, and conducting tissue was 65.7%, 30.5%, and 3.8%, respectively. The conducting tissues were intertwined to form a complex 3D network structure, with a connectivity of 94.77%. The conducting tissue with the largest volume accounted for 60.26% of the total volume of the conducting tissue. The 3D-distribution pattern of the conducting tissue of the node and that of the fibers were similar, but their thickness changed in the opposite pattern. This study revealed the 3D morphometry of the conducting tissue and fibers of the bamboo node, the reconstruction of the skeleton made the morphology more intuitive. Quantitative indicators such as the 3D volume, proportion, and connectivity of each type of tissue was obtained, the bamboo node was enlarged mainly caused by the particularly developed fibers. This work laid the foundation for a better understanding of the mechanical properties and water transportation of bamboo and revealed the mystery of bamboo node shedding of Q. tumidinoda.

Relationship Between the Vascular Bundle Structure of Panicle Branches and the Filling of Inferior Spikelets in Large-Panicle Japonica Rice

The vascular bundles of rice panicles serve to connect the source and the sink, as well as serving as a channel for the transportation of materials. In this study, two homozygous japonica rice strains were used as materials. The vascular bundle structures of the branches in different positions within a rice panicle were observed, and their cross-sectional areas were calculated. In addition, the ultrastructure of the central large vascular bundle (LVB) phloem in the rachillae of superior spikelets (SS) and inferior spikelets (IS) was observed during the grain filling period. Moreover, the soluble sugar and protein contents of the SS and IS rachillae were also measured to study whether the differences in the structure of vascular bundles of the branches were related to the plumpness of grain at different positions. The results showed that vascular bundle cross-sectional areas of the basal primary branches were greater than those in the upper primary branches. Moreover, there was little difference in the areas of vascular bundles between the basal secondary branches and upper secondary branches. However, the vascular bundle areas of the IS rachillae were lower than those in the SS rachillae. Therefore, we believe that the poor vascular tissue channel of the IS rachillae could be the limiting factor in IS plumpness. The results also showed that a similar time course in the degradation pattern of some organelles of the sieve elements and companion cells in central LVB was observed in the SS rachillae and IS rachillae during the grain filling period. Compared with the IS rachillae, more abundant mitochondria and plasmodesmata were found in the companion cells of SS rachillae at the beginning of the filling stage, while no significant differences between SS and IS rachillae were identified at the middle and late filling stages, which implies that the SS rachillae were relatively more effective at transportation compared with the IS rachillae at the initial filling stage. Therefore, the undeveloped vascular bundles of the IS rachillae and their poor physiology and lack of ability to transport at the initial filling stages could be the limiting factor in IS plumpness.

Quantitative Characterization of Bamboo Cortex’structure Based on X-ray Microtomography

Bamboo is a natural fiber composite with layered structure. Millions of years of evolution have endowed bamboo with the most effective structure in nature. The ingenious microstructure provides bamboo with excellent mechanical properties. Bamboo culm is composed of the cortex, a middle layer, and a pith ring. The cortex refers to the area starting from the periphery of the culm wall to the vascular bundles. The present study obtained the two-dimensional microstructure of bamboo cortex cells by optical microscopy and characterized the three-dimensional structure through high-resolution X-ray microtomography (µCT). Based on the analysis, the bamboo cortex cells were classified into four layers: epidermis layer, hypodermis layer, transitional layer, and parenchyma layer. The average pore volume of the bamboo cortex was about 1.54×10-6 mm3, the porosity was 36.1%, and the relative density was 0.639. The epidermis layer, hypodermis layer, transition layer, and parenchyma layer cells had a cell cavity volume of 917.81 µm3, 714.22 µm3, 1258.19 µm3, and 3117.65 µm3, respectively, an average length3d (L) of 19.38 µm, 25.84 µm, 26.46 µm, and 34.88 µm, respectively, an average breadth3d (W) of 14.11 µm, 9.44 µm, 15.22 µm, and 16.6 µm, respectively, and sphericity of 0.85, 0.76, 0.75, and 0.78, respectively. Studies on bamboo anatomical structure, especially three-dimensional digital characterization, will enrich the bamboo microstructure database. Besides, the three-dimensional structure of the bamboo cortex revealed in this study can provide a reference for optimizing composite material hierarchy and biomimetic design.

Root Rot of Codonopsis tangshen Caused by Ilyonectria robusta In Chongqing, China

Codonopsis tangshen Oliv. belongs to the Campanulaceae, it is one of the most important economically medicinal materials in China.Which is used in medical and agricultural applications (Wu Q N, et al. 2020). In August 2019, root rot of C. tangshen was firstly observed in Fengjie, Chongqing city, southwest China (30°45′ 59″ N; 109°36′36″ E; ), causing approximately 20% yield loss. At the initial stage of the disease, the above-ground stems and leaves turn yellow, and brown to black spots of different sizes appear at the base or root of the stem. With the further development of the disease, the above-ground leaves gradually turn yellow as the diseased spots rot from bottom to top, so that they die, and the diseased spots on the roots expand and begin to rot. Generally, they gradually rot from the bottom up, but the vascular bundles are occasionally normal. If the symptoms of C.tangshen started too late, and the root has not completely rotted by late autumn (late October to early November), the rest part of C.tangshen root will not continue to rot, and it is called half C.tangshen. In the next spring, the halfC. tangshen can continue to sprout, but it will continue to rot, which will seriously affect the yield and quality. In order to identify the pathogen, 25 samples of diseased plants were collected and symptomatic rhizome tissues were surface disinfected with 0.1% HgCl2 solution for 30s, rinsed in sterilized water 3 times, placed on potato dextrose agar (PDA), and incubated at 25℃±1°C in the dark. On the PDA, after seven days of culture, the center appeared light yellow, the edges were white, and the aerial hyphae were felt-like. The surface of the colony was reddish-brown and the margins were white and regular. The conidiophores were simple, usually born on the lateral or apical sides of aerial mycelium, unbranched, or minimally branched. Conidia were abundant, cylindrical, or rod-shaped, straight or slightly curved, usually with 1–3 septa. Macroconidia varied in size depending on the number of cells as follows: one-septate 15.3–26.3×4.2–7.3 μm（n=50）μm, two-septate 20.5-30.5×4.9-7.8μm (n=50), and three-septate 29.3–38.5×5.5–7.4 μm (n=50), round at both ends. For molecular identification, DNA was extracted from a representative isolate using a fungus genomic DNA extraction kit (Solarbio, Beijing, China). The internal transcribed spacer (ITS)(ITS1/ITS4, White, et al. 1990), beta-tubulin (TUB2)(BT2A/BT2B, O’Donnell and Cigelnik 1997), translation elongation factor 1-a (TEF) （ EF446F/EF1035R, Inderbitzin et al. 2005), DNA-dependent RNA polymerase subunit II gene(RPB2, O'Donnell K., et al. 2010 ) and histone H3(HIS3) (CYLH3F/CYLH3R, Crous, et al. 2004b) were amplified. BLAST results indicated that the ITS, TUB2, TEF, HIS3, and RPB2 sequences (GenBank MW392103, MW386994, MW386995 MW392103, and MW915473) showed 96% to 100% identity with Ilyonectria robusta sequences at NCBI (GenBank KU350726, JF335378, MN833103, MN833113, KM232336). The phylogenetic tree was inferred from the combined datasets (ITS, TEF1, TUB, and HIS3) from members of the I. robusta species complex analyzed in this study (Cabral et al. 2012 ). To complete Koch's postulates, a conidial suspension (106 spores/ml) collected from isolate CQ13 was irrigated onto fifteen annual C.tangshen potted plants. Sterile water was used as a negative control, and the pathogenicity assay was repeated three times. Following inoculation, the plants were cultured for 9 days at 75% relative humidity and 25 ℃. The inoculated plants showed symptoms similar to those observed in the field. In contrast, the negative control plants were healthy and unaffected. I. robusta was re-isolated from the infected tissues and identified by morphological characteristics and DNA sequence analysis. To our knowledge, this is the first report of I. robusta causing root rot disease of C.tangshen in China. Our results may help to take appropriate steps to control the disease in the commercial area of C.tangshen. The authors declare no conflict of interest.